Updated Sea Ice Products for the NIMBUS 5 Electrically Scanning Microwave Radiometer data from 1972–1977

The Electrically Scanning Microwave Radiometer (ESMR) instrument onboard the NIMBUS 5 satellite was a one-channel microwave radiometer that measured the 19.35 GHz horizontally polarized brightness temperature (TB) from 11 December 1972 to 16 May 1977.Kolbe et. al. (2024) reprocessed this data in order to derive sea Ice concentration for the period and showed that sea ice extend and concentration was indeed recoverable, but one major challenge was that the implemented one-channel algorithm was unable to distinguish first year ice and multiyear ice, resulting in ambiguity between areas with multi-year ice, and areas with low sea ice concentration. Furthermore, since publishing, we have found the applied filtering to be removing too much data, especially after 1975, and on top of that, we have resolved minor data issues.Two datesets are uploaded here, split in to 4 files ;1) A reprocessed version of the data using the methods of Kolbe et. al. (2024), but with some corrections to the output and a new filtering scheme. This is a direct update to https://doi.org/10.5285/34a15b96f1134d9e95b9e486d74e49cf.2) A post processed dataset (LDTPcorrected) where a local dynamical tie point framework has been applied, which resolves the ambiguity by enforcing stability of tiepoints over time.For each dataset a file for each hemisphere (Northern Hemisphere, NH, and Southern Hemisphere (SH)) can be downloadet.The dataset is created using the code available in the referenced github repository https://github.com/EHTellefsen/N5ESMR-SIC-processing

本数据集依托NIMBUS 5卫星搭载的电扫描微波辐射计（Electrically Scanning Microwave Radiometer, ESMR）生成，该仪器为单通道微波辐射计，于1972年12月11日至1977年5月16日期间，测量19.35 GHz水平极化亮度温度（TB）。Kolbe等人（2024）曾对该数据开展再处理以反演对应时段的海冰浓度，研究证实海冰范围与浓度确实可被有效还原，但存在一项核心局限：所采用的单通道算法无法区分一年冰与多年冰，导致多年冰区域与低海冰浓度区域之间出现识别歧义。此外，在该成果发表后，我们发现原使用的滤波算法滤除了过多有效数据，尤其是1975年之后的观测数据；除此之外，我们还修复了少量数据瑕疵。本次共上传两个数据集，分为4个文件：1）基于Kolbe等人（2024）的方法再处理的数据集，对输出结果进行了修正并采用了全新的滤波方案。该数据集是对https://doi.org/10.5285/34a15b96f1134d9e95b9e486d74e49cf的直接更新。2）后处理数据集（LDTP校正版），该数据集采用了局地动态控制点框架，通过强制控制点随时间保持稳定，解决了上述识别歧义问题。每个数据集均包含对应两个半球（北半球（NH）与南半球（SH））的数据文件，可单独下载。本数据集的生成代码可在已引用的GitHub仓库https://github.com/EHTellefsen/N5ESMR-SIC-processing中获取。